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Full text of "The manufacture and properties of iron and steel"

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170
METALLUKGY OF IBON AND STEEL.
	Per 1 pound carbon.	
	Old way.	Dellwik.
Water gas, cubic feet ......	21.7 3627 48.0	44 7 7465 92.5
Heat units ...............		
Per cent, utilized ...........		
		
SEC. IXd.—Heating.furnaces.                     ,
(a)  Soaking pits.—In the steel plants of Europe no coal is used to heat the ingots in the blooming-mill, but in a Gjers soaking pit they heat themselves from internal heat.
(b)  Regenerative furnaces.—Regenerative furnaces are generally used for heating ingots or blooms when these ingots or blooms are red hot to start with.   Ingot furnaces in America resemble a Gjers soaking pit and are operated in much the same manner, small quantities of gas and air being admitted.   The coal used need not exceed 40 pounds per ton, and half this amount is sufficient.
(c)  Reverberatory  furnaces.—A reverberatory  furnace is one in which the fire is at one end, the stack at the  other,  and the   stock is placed on the hearth between, the  flame passing over the top of whatever is placed upon the hearth.    Such furnaces are quite generally used for' heating cold blooms or billets, but their operation is far from perfect, for when a full heat of cold stock is charged, the absorption of heat is so great that combustion is retarded and a clear hot flame cannot be obtained.   At a later period of the operation, when the blooms are hot, a clear flame cannot be carried, as the metal would be oxidized.   During the advanced stages, it is necessary to run a smoky flame, and as the blooms are of nearly the same temperature as the flame, very little heat is utilized in the.furnace, but most of the energy passes out the flue. After the blooms have reached their proper state and while they are being drawn all the heat entering the furnace goes out the stack.   In ordinary reverberatory furnaces the amount of fuel used to heat a ton of steel is twenty times as much as theory would call for.   One way of getting more perfect combustion is to introduce air at the bridge wall, but this often results in loss, as the flame will be sharp and the metal be oxidized.   A loss of only 1 or 2 per cent, of steel will more than balance any saving in fuel,   ..
Where coal is cheap the flame from the heating furnace is often